No one is prying. He is making a moral argument, not conducting surveillance.
How is your life effected if a responsible, married couple decides to use preventative contraception?
One of the points at issue is what constitutes "responsible" in the first place, so you're begging the question.
A culture that encourages and reinforces an attitude that is hostile to life and hostile to God's will is no good for everyone.
The point is that this "responsible" couple is first and foremost hurting themselves.